Political analysts estimate this year's presidential election campaign in the United States will cost about $1 billion, and much of that money will be spent on television advertising. How are the campaigns able to raise so much money, and are the TV commercials having an impact on how Americans vote on Election Day?

Traditionally, in the primary campaign for the American presidency, candidates have received matching grants from the federal government for the money they raise from the private sector to finance their campaigns.

President Bush and Democratic Party presidential nominee John Kerry both decided during this year's primary election campaigns not to accept federal funds, because neither wanted to comply with spending limits candidates must agree to before accepting public money.

This allowed supporters of both candidates to each contribute up to two-thousand-dollars. Early in the year, most analysts predicted that President Bush and his Republican Party would raise far more money than the Democrats.

But Senator John Kerry surprised many political experts with sweeping victories in the primaries, and emerged as the favorite for the Democratic nomination.

Political Science professor Stephen Wayne of Georgetown University says those victories helped Mr. Kerry to erase the early fundraising advantage enjoyed by the Republicans.

"[Mr.] Kerry began raising lots of money after he was the leading Democratic candidate. And the bottom line is, he's raised more money than George W. Bush," explained Mr. Wayne. "The Democrats and Republicans combined have raised over $600 million for this campaign. Now, that money has to be spent before they are nominated for president. Both candidates have chosen to accept the federal funds for the general election, which is $75 million for each of the candidates."

Formal fundraising is only one way money is being raised by those interested in influencing the presidential campaign.

In this year's election, special interest groups have formed so-called 527 organizations, named after a section of the U.S. tax law. These groups are spending enormous amounts of money, primarily on television advertising.

"The 527's are, in essence, a creation of campaign finance reform," says Larry Sabato, a political analyst and the director of the University of Virginia's Center for Politics in Charlottesville. "The reformers told us that we would lose all that independent spending. The reformers, as usual, have turned out to be wrong, because the best minds in America are concentrated in competitive, partisan politics. They always find a way around the law, and lawyers have done it again. The 527's are spending hundreds-of-millions of dollars outside the law, essentially, but still under the law, under the first amendment, to support or oppose Kerry and Bush."

First voice: "I know John Kerry is lying about his first Purple Heart, because I treated him for that injury."

Second voice:" John Kerry lied to get his Bronze Star. I know. I was there. I saw what happened."

Many analysts say one of the most effective TV commercials during this political season was paid for by a veteran's group questioning Senator Kerry's military service and the medals he was awarded during the Vietnam War.

When the commercials began to run in August, followed by the Republican National Convention, polls showed a surge for President Bush. The race had been a virtual tie.

After debating whether to answer the accusations, the Kerry campaign fired off its response in another television commercial.

First voice: "The people attacking John Kerry's war record are funded by Bush's big money supporters. Listen to someone who was there - the man whose life John Kerry saved."

Second voice: It [enemy fire] blew me off the boat. All these Vietcong were shooting at me. I expected I'd be shot when he pulled me out of the river. He risked his life to save mine."

Dennis Johnson, a professor of political management at George Washington University, says such negative attacks do work. "What we found in the month of August, when these ads started hitting the airwaves, and then when Kerry started attacking back, that Kerry's approval rate for what kind of commander-in-chief would he be, or how would he be able to handle the war, went down," said Mr. Johnson. "Apparently this took hold in many people's minds, particularly veterans, that perhaps John Kerry isn't the right man to lead the country. So I think we'll find that, if it's the right kind of message, delivered by these outside groups, it can certainly hurt them."

By the November second election, analysts say, about two-thirds of all the money raised by the candidates will be spent on television advertising.

That advertising will be purchased in television markets in what are called battleground states, where public opinion polls show the race between President Bush and Senator Kerry is very close.